What's wrong with this? It's a very subtle problem. I'll give you a moment to think about it, and a video to see if you notice the problem. Make sure you don't cheat.

(demonstrating removal of flicker in QML)

Back already? Have you figured it out? That's right, it flickers. Horrifically.

So what causes this? By default, QWidgets are drawn parent first, with parents drawing children. When a widget is drawn, first, it draws its background, then it draws the actual content. That background proves to be a problem, in this case.

If we add the following lines to the above example, the flicker goes away, and my eyes no longer want to bleed:

NB: on Harmattan (and Nemo Mobile) at least, make sure you always use QWidget::showFullScreen(). The compositor in use there unredirects fullscreen windows (meaning no compositor in the way), so you get faster drawing performance, and every frame counts.

The thoughts and opinions of an open source & mobile gadget enthusiast who ran away from Australia and is now surviving in the middle of nowhere in Norway while learning how to love snow, ice, and all things Scandinavian.